English Views: 5 Author: Site Editor Publish Time: 2022-04-01 Origin: Site
Process principle of cold-rolled stack pre-treatment: The process principle of cold-rolled stack pre-treatment is the same as that of conventional de-scouring and bleaching pre-treatment process, but the reaction conditions during the treatment process are milder. Therefore, the amount of additives in the production process should be In order to ensure the stability and effectiveness of the pre-treatment quality, it is necessary to add some pre-treatment auxiliaries. According to the purpose of the pre-treatment of cold rolling stock and the different processes and stacking conditions, the pre-treatment process of cold rolling stockpiling can be divided into: pre-treatment desizing process for cold rolling stocking, scouring process for pre-treatment for cold rolling stocking, pre-treatment for cold rolling stocking Desizing, scouring process, desizing, scouring and bleaching process before cold rolling pile.
In the pretreatment process of cold rolling stack, the stacking time is a very important process parameter. The stacking time used in actual production is: 8h, 12h, 16h, 24h, etc. As for why this stacking time is adopted, few people pay attention and think about it, and the current process parameters are often formulated based on past "experience".
1. Factors affecting the stacking time: the concentration of additives in the working solution, the actual amount of liquid carried by the fabric, the stacking temperature, the stacking time, the tissue structure of the fabric, the impurities in the fabric, and the maturity of the cotton fiber.
(1) The concentration of auxiliaries in the working solution is adjusted according to the tissue specifications and process requirements of the fabric. The classification of the treatment process should not be too finely divided, otherwise there will be certain difficulties in the adjustment and control in the production process.
(2) The amount of liquid in the pre-treatment of cold-rolling piles is better if there is a little foam at both ends of the cloth roll and the working fluid overflows when the above rolls are carried out. Too much liquid will cause the cloth roll to slip off easily; if the liquid is too small, it will affect the quality of refining and bleaching. Therefore, for a specific fabric, the amount of liquid carried is determined and can be adjusted at will, but the actual production process does not pay enough attention to this aspect.
(3) The stacking temperature before cold rolling stacking is to adopt the method of normal temperature stacking or 30~35°C thermal insulation stacking.
(4) The stacking time of the cold-rolled stacking pretreatment has a certain independence, and its adjustment is relatively convenient and will not cause adverse effects on other batches. In the entire cold-rolled stacking pretreatment process parameters, by adjusting the stacking time It is the most effective and convenient to realize the individual control of the pretreatment quality of different products.
(5) Differences in the tissue structure of the fabric, the impurity content of the fabric, and the maturity of the cotton fiber have an impact on the quality of pretreatment, but it is indeed difficult to detect them in actual production. It is enough to set the time to control the quality of the pretreatment and meet the quality requirements of the post-processing.
2. The principles for formulating the process parameters of the fabric cold rolling stack:
(1) The quality of the pre-treatment should be able to meet the processing quality requirements of the post-process.
(2) The process parameters should be selected in the range where the fluctuation of product quality is relatively moderate, so that the process parameters have a certain tolerance to ensure the stability and repeatability of the product.
(3) The control of different products and different quality requirements is realized by adjusting the stacking time.
3. The basis for formulating the stacking time: Before formulating the large-scale production process, a small sample stacking experiment should be carried out. After the padding working fluid of the small sample, it should also be stacked according to the requirements of the large sample. The stacking time can be set from 12 to 48h. A total of 10 A comparative experiment was carried out on the different files, and the stacking time period with higher stability was selected as the stacking time for mass production.
Liquid level control of working fluid: During the production process, fresh supplementary fluid should be added evenly from the back of the cloth outlet to ensure that the concentration of the working fluid taken away by the fabric is stable and consistent; Consistency and stability of actual carry volume.
The control of the amount of liquid in the pre-treatment of cold-rolled stacking: The pre-treatment of cold-rolled stacking is generally to directly pad the alkaline oxygen working solution after the grey cloth is singed. Because the grey cloth contains natural impurities and pulp, the fabric has a certain water repellency, so, When the fabric is padding with the working fluid, the permeability and water holding capacity are very poor, and the actual liquid carrying amount of the fabric is also low. In the pretreatment process of cold pad stacking, the amount of liquid in fabric padding is different from that in pad dyeing, because after padding the working solution, there is a "drainage" problem in the process of coiling and stacking, that is, the fabric The working fluid on the surface layer will be squeezed out of the cloth roll during the rolling and stacking process. The effective liquid carrying amount of the fabric refers to the actual liquid carrying amount during the stacking process after the fabric is rolled up, that is, the weight of the working liquid that penetrates inside the fabric and the fibers are cohesive, not the liquid carrying liquid after the fabric is padded with the working liquid before rolling. quantity. In the pre-treatment process of cold-rolled pile, only the actual liquid amount of the fabric has practical significance for the quality of refining and bleaching, which is often confused and ignored in actual production. The guide rollers in the working fluid rolling groove are divided into four upper and lower three, with a diameter of 150~200mm, and the two upper guide rollers should be equipped with pressurized pressure rollers. The rolling car should use large-diameter rolls to reduce the difference in the amount of liquid between the left, middle and right due to the deformation of the rolls during the production process. The A-frame rolls should not be too heavy to avoid too much "drainage". When winding up, the amount of liquid in the fabric should be controlled so that there is a little foam at both ends of the cloth roll and the working fluid overflows. If the liquid is too much, the cloth roll is easy to slip off; Too little liquid will affect the quality of bleaching.
1. The method of multi-dipping and multi-rolling should be adopted to ensure uniform penetration of the working fluid. Generally, two-tank padding method is adopted, the front tank uses a three-roll heavy-duty rolling car, and the rear tank uses a two-roller rolling car. The working fluid is added from the back tank and flows back to the front tank to ensure that the working fluid carried by the fabric is fresh.
2. Pay attention to the stable and consistent pressure of the two-roll rolling car, keep the same amount of liquid, and keep the stacking time and stacking temperature of each cloth coil consistent, which will be beneficial to the effect of cold rolling stacking.
3. In actual production, it is difficult to achieve the consistency of the pre-treatment effect of the fabric in the pre-treatment process of the cold stack, because the defects in the design of the processing technology will inevitably lead to fluctuations in the quality of the pre-treatment, and the error of this process design reflects In the following aspects: First, the fabric is first-in-last-out when the cold-rolled stack is rolled into the desizing and washed, and the stacking time difference before and after the roll length of the conventional product is calculated at about 2.5h or longer. Second, there is a difference between the speed of the cold-rolled stack and the speed of the pre-treatment, uncoiling, and alkali washing. Often, the speed of the cold-rolled stack (about 70m/min) is faster than the speed of the heat treatment (about 50m/min). The difference between roll-to-roll of the whole batch of fabric in the roll-to-roll process, and the difference between the front and the back of the fabric in the same roll. Third, the difference in the amount of liquid in the left and right and the middle of the cold roll stack and the cloth roll is often caused by two aspects: the difference in the amount of liquid produced by the pressure difference between the two sides of the roll and the middle of the rolling machine; during the stacking process. The working fluid on both sides leaks out due to the action of pressure and gravity, resulting in a difference in the amount of fluid on the left, middle and right sides of the fabric. Fourth, the temperature difference between the inside and outside of the roll, the two sides and the middle. The existence of these differences will inevitably lead to differences in the pretreatment effect of the fabrics. When these differences are superimposed and accumulated to a certain extent, there will be obvious differences in the subsequent related processes.
